1. Field of the Invention
The present invention relates to a movement condition computing device, which computes movement distance information or movement velocity information on a mobile body even when velocity information on the velocity of the mobile body cannot be acquired during travel of the mobile body, and also relates to a movement condition computing method, a movement condition computing program, a recording medium recording this program, and a navigation device.
2. Description of Related Art
Vehicle-installed navigation devices have been known since prior, and such a device is installed in a vehicle, which is mobile body, for detection of the vehicle""s present position and display of the vehicle""s present position on a map.
This vehicle-installed navigation device is equipped with a GPS receiver, a computing device, a map storage device, and a display device.
With this vehicle-installed navigation device, the abovementioned computing device generates distance information and traveling direction information on the vehicle based on sensor outputs output from a vehicle velocity sensor and a yaw rate sensor.
Also, this vehicle-installed navigation device detects a relative movement distance and a relative movement direction of the vehicle at each unit time based on the distance information and traveling direction information. The navigation device then computes the present position of the vehicle from position information obtained from the GPS receiver and position information obtained based on the relative movement distance and relative movement direction. Thereafter, the map information stored in the map storage device is read and the computed present position is overlapped onto and displayed along with the map information.
In recent years, due to an increased inclination towards vehicle safety, preventive safety devices have come to be equipped in vehicles. Many vehicles are already equipped with an ABS (Anti-lock Brake System), which is a representative form of preventive safety device.
A vehicle velocity pulse signal, which the abovementioned vehicle velocity sensor acquires from a vehicle, may take on various forms, such as that acquired from a speedometer-related part of the vehicle, that acquired from an abovementioned ABS-related part, etc. In a specific example, which is employed in some vehicle models and in which a vehicle velocity pulse signal is acquired from an ABS-related part, an ABS sensor is mounted to a hub unit used at a wheel of a vehicle and the rotation speed of this wheel is detected. Based on this detected rotation speed, a sensor signal is output to an ECU (Electric Control Unit) of the vehicle. Thereafter, this ECU outputs the input sensor signal as the vehicle velocity pulse signal, etc.
Here, the vehicle velocity sensor, which is equipped in the vehicle-installed navigation device, detects this vehicle velocity pulse signal and the abovementioned computing device detects the leading edges or trailing edges of the detected vehicle velocity pulse signal and computes the number of pulses. A predetermined distance factor is then used to compute the relative movement distance of the vehicle by the following [Equation 1].
Relative movement distance=Number of vehicle velocity pulsesxc3x97Distance factorxe2x80x83xe2x80x83[Equation 1]
However, with an ABS sensor, when a vehicle is traveling at low velocity, a state in which the wheel is rotating cannot be distinguished from a state in which the wheel is locked. That is, a sensor signal will not be output from the ABS sensor to an ECU in this case. The ECU thus cannot generate the vehicle velocity pulse signal when the vehicle is traveling at less than or equal to a predetermined velocity.
In this case, the vehicle-installed navigation device also cannot acquire the vehicle velocity pulse signal when the vehicle is traveling at less than or equal to the predetermined velocity. That is, when a vehicle is traveling at less than or equal to the predetermined velocity, the relative movement distance or relative movement velocity of the vehicle cannot be computed.
A main object of the present invention is to provide a movement condition computing device, which can appropriately compute the relative movement distance or relative movement velocity of a mobile body as well as a movement condition computing method, a movement condition computing program, a recording medium recording this program, and a navigation device.
This invention""s movement condition computing device comprises: a velocity information acquisition section, acquiring velocity information concerning the velocity of a mobile body; a minimum output velocity computing section, computing, when the abovementioned velocity information acquisition section cannot acquire the abovementioned velocity information during movement of the abovementioned mobile body, a minimum output velocity of a point in time at which the abovementioned velocity information acquisition section could acquire the abovementioned velocity information; a state information acquisition section, acquiring state information on at least one of start and stop states of the abovementioned mobile body; and a movement condition computing section, computing at least one of movement distance information and movement velocity information on the abovementioned mobile body based on the minimum output velocity computed by the abovementioned minimum output velocity computing section and the state information acquired by the abovementioned state information acquisition section.
This invention""s movement condition computing device comprises: a velocity information acquisition section, acquiring velocity information concerning the velocity of a mobile body; an acceleration information acquisition section, acquiring acceleration information concerning the acceleration of the abovementioned mobile body; and a movement condition computing section, computing, when the abovementioned velocity information acquisition section cannot acquire the abovementioned velocity information during movement of the abovementioned mobile body, at least one of movement distance information and movement velocity information on the abovementioned mobile body based on the acceleration information acquired by the abovementioned acceleration information acquisition section.
This invention""s movement condition computing method comprises the steps of: acquiring velocity information concerning the velocity of a mobile body; computing, when the abovementioned velocity information cannot be acquired during movement of the abovementioned mobile body, a minimum output velocity of a point in time at which the abovementioned velocity information could be acquired; acquiring state information concerning at least one of start and stop states of the abovementioned mobile body; and computing at least one of movement distance information and movement velocity information on the abovementioned mobile body based on the abovementioned minimum output velocity that has been computed and the abovementioned state information that has been acquired.
This invention""s program is a movement condition computing program, characterized in making a computer execute this invention""s movement condition computing method described above.
This invention""s recording medium is a recording medium recording a movement condition computing program characterized in storing this invention""s movement condition computing program described above in a manner enabling reading by a computer.
This invention""s navigation device comprises: this invention""s movement condition computing device described above; and a present position determination section, determining the present position of a mobile body based on movement distance information and movement velocity information computed by the movement condition computing device.